#include <iostream>
using namespace std;

double s;
double x = 2;
int count = 1;

int main()
{
    cin >> s;
    double sum = 2;
    if(s <= 2) 
    {
        cout << 1 << endl;
        return 0;
    }
    
    while(sum < s)
    {
        x *= 0.98;
        sum += x;
        count ++;
    }
    cout << count << endl;
    return 0;
}